1. Field of the Invention
The present invention relates to the odorization of odorless gases and, more particularly, to a gas scrubbing device for providing odorant vapor filtration during regular operation, maintenance and failure of odorant delivery equipment used in the odorization of an odorless gas.
2. Description of the Prior Art
Odorants are added to odorless gases, such as natural gas, so that they can be detected easily by smell. Conventional odorants include mercaptans, methyl sulfides, aliphatic sulfides, dimethylsulfide as well as various blends of other commonly accepted chemicals. Odorants used with natural gas are extremely odiferous and volatile, so that only a small amount of liquid is needed to odorize a relatively large volume of natural gas.
Various techniques have been developed for odorizing natural gas. One technique consists of injecting liquid odorant directly into the natural gas pipeline. A high pressure injection pump draws odorants from a liquid storage tank into the gas pipeline where the odorants evaporate throughout the gas in the pipeline. Liquid odorant pressure is typically stepped down in the injection system and the released pressure is directed into an expansion tank. At regular intervals, gas is released from the expansion tank so as to maintain the pressure within the expansion tank under a predetermined pressure threshold. The gas released from the expansion tank is passed through a filter before being discharged as an odorant-free gas.
A second technique for odorizing natural gas consists of bypassing a small amount of natural gas through a tank containing liquid odorant. The bypass gas leaves the tank saturated with odorant gas and is then returned back into the main gas pipeline where it diffuses throughout the pipeline. The odorizing equipment is typically depressurized during odorant re-fill and the released odorant gas is typically flared or filtered by adsorption before being discharged as a non-toxic odorless gas.
Often the failure of such odorizing equipment results in odorant being released into the surrounding environment. Servicing operations on the equipment and re-filling of the storage tank is also generally associated with the release of odoriferous gases into the atmosphere. Due to the dangerous nature of odorous gases and the ever increasing sensitivity of public to odors, it is essential to minimize odorant smell releases, which are not associated with leaks of the natural gas distribution system. Heretofore, there has been very little protection to prevent odorous gases from escaping into the environment as a result of equipment failure, maintenance operations and small spills of liquid odorant during re-filling of the storage tank.
It would thus be desirable to provide a new gas scrubbing device which is adapted to scrub odorants from the air at the odorization site as well as filter excess odorant gases before being vented from the odorizing system.
It is therefore an aim of the present invention to provide a gas scrubbing device that can be used for filtering the air at an odorization site as well as for filtering odorant gases before being released from the system.
It is also an aim of the present invention to provide odorant vapor scrubbing through the use of a single unit capable of scrubbing odorant vapors from minimal through flow to relatively high gas through flow.
It is a further aim of the present invention to provide a gas scrubbing device adapted to scrub very low concentration of odorant gases.
It is a still further aim of the present invention to provide a gas scrubbing device adapted to prevent release of odor into the environment during regular operation of an odorant delivery system as well as during maintenance and failure of the system.
Therefore, in accordance with the present invention, there is provided a multi-operation mode gas scrubbing device for removing odorous gases released during the regular operation of an odorant delivery system as well as during the maintenance and failure of the system, the device comprises a tank housing a filtration medium for adsorbing odorous gases, normally-open main inlet and main outlet adapted to be connected in fluid flow communication with the odorant delivery system for removing odorous gases from a gas stream during normal operation conditions, a normally-closed maintenance/emergency inlet openable under maintenance and emergency conditions for allowing odorous gas released from the odorant delivery system into the surrounding environment to be drawn through the filtration medium, and an air mover connected to a normally-closed maintenance/emergency outlet of the tank for drawing, through said filtration medium via said normally-closed maintenance/emergency inlet, the odorous gases released from the system, thereby preventing release of odors into environment during maintenance and failure of the system.
In accordance with a further general aspect of the present invention, there is provided a multi-operation mode gas scrubbing device for use with odorizing equipment, comprising a tank housing a filter medium, a pair of normally-open inlet and outlet adapted to be connected in flow communication with the odorizing equipment for providing for passive scrubbing of odorant vapors generated during regular operation of the odorant delivery system, and a pair of normally-closed inlet and outlet adapted to be opened under maintenance, re-fill, or emergency conditions for providing for active odorant vapor filtration of the odorant vapors released in the environment surrounding the odorizing equipment, said normally-closed outlet being adapted to be operatively connected to an air mover for drawing outside air through said normally-closed inlet.
In accordance with a still further general aspect of the present invention, there is provided a multi-operation mode gas scrubbing device for removing odorous gases released during the regular operation of an odorant delivery system as well as during the maintenance and failure of the system, the device comprises a tank housing a filtration medium for absorbing odorous gases, a normally-open main inlet adapted to be connected in fluid flow communication with the odorant delivery system for removing odorous gases from a gas stream during normal operation conditions, a normally-closed maintenance/emergency inlet openable under maintenance and emergency conditions for allowing odorous gas released from the odorant delivery system into the surrounding environment to be drawn through the filtration medium, and an air mover connected to an outlet of the tank for drawing the odorous gases released from the system through said filtration medium via said normally-closed maintenance/emergency inlet, thereby preventing release of odors into environment during maintenance and failure of the system.
According to a further aspect of the present invention, suction (air through flow) is generated by either electrical fans or by air amplifier mounted either on top of the filter or preferably on the maintenance vehicle servicing the station(s). The apparatus has the capacity to prevent release of odor into the environment at the regular operating conditions, during maintenance, re-fill, or failure of the equipment, and in the case of spills of limited quantities of liquid odorants.
According to a present invention, odorant gases are removed from natural gas or air streams by means of adsorption on an activated carbon substrate. The carbon filter is combining capability of passive filter for capturing vapors of odorants during the regular operation of odorant delivery equipment or related equipment, with capacity for eliminating odorant vapors from escaping into environment during maintenance, re-fill, and failure of such equipment and also during emergencies due to liquid spills. The proposed invention allows for work in hazardous environment (presence of natural gas) by using nitrogen or air powered variable air amplifier (Venturi) systems, by moving suction systems out of hazardous area or using explosion proof suction devices.